1. [Technical Field of the Invention]
The present invention relates to an optical range finder. More specifically, the invention relates to a mounting structure of a compact optical range finder incorporated in a camera or the like to be used for automatic focus adjustment.
2. [Prior Art]
A compact optical range finder mounted on a camera or the like is basically provided with a projection unit, a detection unit, a holding frame, and a support substrate to measure a distance to an object in an optical axis direction. The projection unit projects luminous flux to the object located in the optical axis direction. The detection unit receives the luminous flux returned from the object. The holding frame is made of a molded article or the like, and integrally incorporates the projection unit and the detection unit. The protective holding frame is mounted on the support substrate, and a necessary electronic component such as an IC is attached to the support substrate.
The projection unit is constituted of a lens, a light emitting element, and a backside substrate. The lens is mounted to a front side of the holding frame to converge the luminous flux in the optical axis direction. The light emitting element is constituted of an infrared LED or the like to emit luminous flux to the lens. The backside substrate is mounted to the holding frame to shield the light emitting element from the back side. On the other hand, the detection unit is constituted of a lens, a light receiving element, and a backside substrate. The lens is mounted to the front side of the holding frame to converge the luminous flux returned from the object. The light receiving element is incorporated in the holding frame to receive the luminous flux. The backside substrate is mounted to the holding frame to shield the light receiving element from the back side. Various developments have been made on the camera optical range finder having such a constitution, and mounting structures thereof are disclosed in Japanese Patent Application Laid-Open No. Hei 11 (1999)-133293, Japanese Patent Application Laid-Open No. Hei 11 (1999)-305111, Japanese Patent Application Laid-Open No. 2000-89095, Japanese Patent Application Laid-Open No. 2000-347098, Japanese Patent Application Laid-Open No. 2001-33237, and the like.
The light emitting element and the light receiving element are incorporated in the holding frame, and both are covered with the backside substrates. Accordingly, a constitution is adopted where basically no light leakage occurs from the light emitting element to the light receiving element. However, as there is slight light leakage from the light emitting side to the light receiving side through the support substrate on which the holding frame is mounted, deterioration of measuring accuracy is brought about, which causes an error. A most part of the light emitted from the light emitting element is projected through the lens of the front side to the object. However, there is leaked light, a part of which is leaked through a terminal of the light emitting element to the support substrate and, further, through a thickness part and a surface part of the support substrate to reach the light emitting element. Conventionally, it has been difficult to completely shut off such a leaked light, or much work time and labor have been required for complete shutting-off.
The light emitting element is attached to the holding frame made of the resin molded article. The unit of the light emitting element is inserted into an opening formed beforehand in the holding frame to carry out automatic positioning, and set a predetermined parallax relative to the opposite lens. However, at a point of time when the light emitting element is inserted, it is impossible to check whether the element is surely set in a predetermined position or not. Conventionally, after assembling of the optical range finder, actual measurement has been carried out to check a position of the light emitting element. Since the position of the light emitting element cannot be visually checked at an assembling stage, the impossibility of checking has been an obstacle to work.
In order to solve the foregoing technical problems, the following means has been contrived. That is, the prevent invention has three aspects. According to a first aspect, there is provided an optical range finder for measuring a distance to an object in an optical axis direction, comprising a projection unit for projecting luminous flux to the object located in the optical axis direction, a detection unit for receiving the luminous flux returned from the object, a holding frame that holds therein the projection unit and the detection unit, and a support substrate that supports thereon the holding frame, wherein the projection unit comprises a light emitting element for emitting the luminous flux in the optical axis direction, and a backside substrate fixed to the holding frame to shield the light emitting element from a backside, the detection unit comprises a light receiving element mounted in the holding frame to receive the luminous flux returned from the object, and another backside substrate fixed to the holding frame to shield the light receiving element from a backside, the holding frame has a partition wall for separating the detection unit and the projection unit from each other, an end of the partition wall being provided with a tip protruding from a bottom of the holding frame, and the support substrate is formed with a groove in a surface of the support substrate which comes in contact with the bottom of the holding frame, such that the groove can be engaged with the tip of the partition wall so as to shut off a light leaked from the projection unit through a thickness of the support substrate to the detection unit by a combination of the tip and the groove.
According to a second aspect of the invention, there is provided an optical range finder for measuring a distance to an object in an optical axis direction, comprising a projection unit for projecting luminous flux to the object located in the optical axis direction, a detection unit for receiving the luminous flux returned from the object, a holding frame that holds therein the projection unit and the detection unit, and a support substrate that supports thereon the holding frame, wherein the projection unit comprises a light emitting element for emitting the luminous flux in the optical axis direction, and a backside substrate fixed to the holding frame to shield the light emitting element from a backside, the detection unit comprises a light receiving element mounted in the holding frame to receive the luminous flux returned from the object, and another backside substrate fixed to the holding frame to shield the light receiving element from a backside, the holding frame has a bottom which comes in contact with a surface of the support frame, and a bank part protruding from the bottom to surround the light emitting element housed in the holding frame, and the support substrate has a wiring pattern formed on the surface of the support substrate for electrical connection to the projection unit and the detection unit and a resist pattern selectively formed on the surface of the support substrate, such that at least one of the wiring pattern and the resist pattern is removed from an area aligned with the bank part so as to shut off a leak light traveling the surface of the support substrate from the projection unit to the detection unit.
According to a third aspect of the invention, there is provided an optical range finder for measuring a distance to an object in an optical axis direction, comprising a projection unit for projecting luminous flux to the object located in the optical axis direction, a detection unit for receiving the luminous flux returned from the object, a holding frame that holds therein the projection unit and the detection unit, and a support substrate that supports thereon the holding frame, wherein the projection unit comprises a light emitting element for emitting the luminous flux in the optical axis direction, and a backside substrate fixed to the holding frame to shield the light emitting element from a backside, the detection unit comprises a light receiving element mounted in the holding frame to receive the luminous flux returned from the object, and another backside substrate fixed to the holding frame to shield the light receiving element from a backside, and the holding frame is formed with an opening in a bottom of the holding frame which comes in contact with a surface of the support, the opening being provided for receiving therein the light emitting element and being formed with a guide part for serving as a visual positioning guide when the light emitting element is inserted through the opening into the holding frame.
According to the first aspect of the present invention, the tip of the partition wall formed in the holding frame to separate the projection unit and the detection unit is placed into the support substrate, whereby infiltration of light through a thickness of the substrate is prevented. According to the second aspect of the present invention, the bank part formed on the bottom of the holding frame is engaged with the wire or resist pattern formed on the surface of the support substrate, whereby light infiltrated from the projection unit side through the surface of the substrate to the detection unit side is shut off. Further, according to the third aspect of the present invention, the guide part serving a positioning marker when the light emitting element is inserted through the opening formed in the holding frame is formed beforehand in the opening. Thus, a position can be visually checked immediately after the light emitting element is incorporated. By implementing the above-described measures, it is possible to increase measurement accuracy of the optical range finder.